1. Field of the Invention
The present invention relates to a calibration mechanism, and more particularly to a calibration mechanism of a scanner. The calibration mechanism is disposed in the scanner, and a calibration strip, which travels in reciprocating motion relative to an optical module of the scanner, is disposed in the calibration mechanism. Therefore, image data of a plurality of scanning lines are acquired by the optical module as a light illuminates on the moving calibration strip, and the image data of the scanning lines becomes parameters for the scanner to calibrate the shading of the optical module.
2. Prior Art
Generally, there are two different types of dynamic calibration mechanism for a scanner: one is a stationary calibration strip mounted in a flatbed scanner, such that an optical module of the scanner moves relative to the stationary calibration strip to acquire the image data of the calibration strip; and the other is a movable calibration strip mounted in a feeder or in a scanner with an auto document feeder, such that the movable calibration strip moves relative to an optical module of the feeder.
Referring to FIG. 1, for a dynamic calibration mechanism, a calibration strip 11 is mounted at one end of a flexible member 13, and a roller 15 is connected with the other end of the flexible member 13. By the rotation of the roller 15, the assembly of the flexible member 13 and the calibration strip 11 moves relative to an optical module 17 of the scanner in reciprocal motion. A light source (not shown) illuminates on the moving calibration strip 11, and as the light reflected from the calibration strip 11 is received by the optical module 17, image data of a plurality of scanned lines of the calibration strip 11 is obtained, so as to use the image data as parameters for calibrating the shading of image sensors of the optical module.
Because vertical movement of the flexible member 13 and the calibration strip 11 is not restricted, a vertical drift easily occurs to the calibration strip 11, where the calibration strip 11 moves up and down (shown as dotted line). Thus, as the optical module 17 operates to perform the calibration, different results will be obtained because the vertical position of the calibration strip 11 is not constant.
In order to keep the calibration results correct and consistent, the vertical movement of the calibration strip 11 has to be confined within a certain range when the optical module operates to correct the shading of the image sensors.